The children's Hospital of Philadelphia has contributed to the science of the Children's Cancer Study Group in the last 20 years with regard to patient entry on study, scientific leadership in committees and strategy groups, and the initiation and performance of pilot studies. Specific contributions have been the following: 1) Development of ferritin as a biologic marker of neuroblastoma activity and of a histopathologic classification of neuroblastoma following on the earlier work of Evans and D'Angio in the staging of that disease; 2) Development of a multidisciplinary nero- oncology program consisting of neurosurgery, radiology, radiation therapy, neurology and pediatric oncology, which has developed successful clinical trials for brain tumors when none were available in the Group. These have and will be incorporated into randomized Group trials; 3) Initiation of a method of performing edpidemiologic studies utilizing the random-digit dialing technique and assuming responsibility for Group studies of retinoblastoma and brain tumors through NCI funded grants; 4 Providing leadership ad expertise in developing studies of late effects of cncer therapy; and 5) Performing studies for leukemia, Hodgkin's disease, lymphomas, rhabdomyosarcoma, Wilms' tumor, and brain tumors serving as early pilots for the Group. The investigators participating in this endeavor will continue to provide data of high quality for patients entered on CCG studies annually and more than 1,000 are being followed on study; it is expectd that this number will increase in the future since brain tumor, hodgkin's disease and second-line leukemia sxtudies are now available. Approximately 70 new brain tumor patients and 15 each with Hodgkin's disease and relapsed ALL are seen annually here; at least 50 will be entered on studies not previously available. There are 20 investigators in this institution holding 96 positions on study committees, strategy groups, or scientific committees, 19 of them being in positions of leadership. We will continue to enroll all eligible patients and to coform to group requirements with regard to study participation, in addition to providing leadership in the specific areas noted above.